Step 1: Use identities:\( \sin^{-1}\left(\dfrac{2a}{1+a^2}\right) = 2\tan^{-1} a \),\( \cos^{-1}\left(\dfrac{1-b^2}{1+b^2}\right) = 2\tan^{-1} b \) Step 2:\( 2(\tan^{-1} a - \tan^{-1} b) = 2\tan^{-1} x \) Step 3:\( x = \dfrac{a - b}{1 + ab} \)